LINQ 中的实体附件问题

Entity attachment issues in LINQ(LINQ 中的实体附件问题)

问题描述

我从表单 POST 接收到 LINQ 实体后，尝试将其附加到数据上下文.但是，我得到的只是以下异常:

I am trying to attach a LINQ entity to the data context after I receive it from a form POST. However, all I get is the following exception:

An entity can only be attached as modified without original state if it declares a version member or does not have an update check policy.

我也尝试附加原始行，如下所示:

I have also tried attaching the original row, like so:

dataContext.People.Attach(person, originalPerson);

在这种情况下，我得到以下异常:

In this case, I get the following exception:

Object reference not set to an instance of an object.

这是我的控制器中的代码:

Here's the code in my controller:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Edit(int id, Person person) {
    var prevPerson = dataContext.People.Single(p => p.ID == id);
    dataContext.People.Attach(person, prevPerson);
    dataContext.SubmitChanges();
    return Redirect("~/People/Index");
}

对我在这里做错了什么有任何想法吗?如果需要，我可以发布实体代码.

Any ideas on what I'm doing wrong here? I can post the entity code if needed.

推荐答案

在 LinqToSQL 设计器中，将所有更新检查设置为从不，当你附加时，像这样调用它:

In the LinqToSQL designer set all of the Update Checks to Never and when you attach call it like so:

 context.entity.Attach(entity, true);

或者，您也可以从数据库中获取实体并使用来自 POSTed 实体的数据对其进行更改，然后将其作为更改提交.

Alternatively, you could also grab the entity from the db and change it using the data from the POSTed entity, then submit that as a change.

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